Lead‐free (K,Na)NbO 3 ‐based ceramics with high optical transparency and large energy storage ability

Abstract Highly transparent lead‐free (1‐ x )K 0.5 Na 0.5 NbO 3 – x Sr(Zn 1/3 Nb 2/3 )O 3 (KNN– x SZN) ferroelectric ceramics have been synthesized via a conventional pressureless sintering method. All samples are optically clear, showing high transmittance in the visible and near‐infrared regions (~70% and ~80% at 0.5 mm of thickness, respectively). This exceptionally good transmittance is due to the pseudo‐cubic phase structure as well as the dense and fine‐grained microstructure. In addition, a high energy storage density of 3.0 J/cm 3 has been achieved for the 0.94K 0.5 Na 0.5 NbO 3 –0.06Sr(Zn 1/3 Nb 2/3 )O 3 ceramics with submicron‐sized grains (~136 nm). The main reason is likely to be the typical relaxor‐like behavior characterized by diffuse phase transition, in addition to the dense and fine‐grained microstructure. This study demonstrates that the 0.94K 0.5 Na 0.5 NbO 3 –0.06Sr(Zn 1/3 Nb 2/3 )O 3 ceramic is a promising candidate of lead‐free transparent ferroelectric ceramics for new areas beyond transparent electronic device applications.